Interest in creating rich user experiences on small portable devices has grown in parallel with the proliferation of PDAs and cell-phones built on mature computing platforms. The growth of the computational power of these devices has continued against the relatively constant display and navigation bottlenecks they pose to users. Small portable computing devices only provide a limited view of a given information space. The limited input modalities make it difficult for small form-factor devices to support both incremental and ballistic (rapid navigation towards a target typically initiated by a command or button press) navigation of large datasets. Because these devices are often used in mobile situations where user's attention is divided, interactions that require precise control are challenging.